ZnO nanostructures, including ZnO nano quasi-spheres and nanoplates, were synthesized hydrothermally, via the reaction of zinc acetate and Preyssler type heteropolyacid (H_14 [NaP_5 W_30 O_110 ]), at 140°C for 48 and 72 hours, respectively. The ZnO nanostructures were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The diameter of nano quasi-spheres which was obtained was about 5–10 nm. The nano plates had hexagonal shape showing diameter of 40–60 nm. The results confirmed that the synthesized products are single crystalline with wurtzite hexagonal phase. Photocatalytic degradation of Methylene blue and Congo red was investigated using prepared ZnO nanostructures as above. Prepared nanostructures showed the high performance in photocatalytic degradation and almost 70% decolorization achieved within only 15 min. First order reaction constants were evaluated 0.0745 and 0.0746 for Methylene blue and Congo red degradation reactions, respectively. Consequently it has been concluded that the photocatalytic decolorization followes first order kinetics.
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran.